The present invention relates in general to a carbon nanotube suspension, and more particularly, to a solvent containing carbon nanotube suspending therein. The carbon nanotube suspension can be used for forming an electron-emission source of a field-emission display.
The field-emission display is a very newly developed technology. Being self-illuminant, such type of display does not require a back light source like the liquid crystal display (LCD). In addition to the better brightness, the viewing angle is broader, power consumption is lower, response speed is faster (no residual image), and the operation temperature range is larger. The image quality of the field-emission display is similar to that of the conventional cathode ray tube (CRT) display, while the dimension of the field-emission display is much thinner and lighter compared to the cathode ray tube display. Therefore, it is foreseeable that the field-emission display may replace the liquid crystal display in the market. Further, the fast growing nanotechnology enables nano-material to be applied in the field-emission display, such that the technology of field-emission display will be commercially available.
FIG. 1 shows a conventional triode field-emission display, which includes an anode plate 10 and a cathode plate 20. A spacer 14 is placed in the vacuum region between the anode plate 10 and the cathode plate 20 to provide isolation and support thereof. The anode plate 10 includes an anode substrate 11, an anode conductive layer 12 and a phosphor layer 13. The cathode plate 20 includes a cathode substrate 21, a cathode conductive layer 22, an electron emission layer 23, a dielectric layer 24 and a gate layer 25. A potential difference is provided to the gate layer 25 to induce electron beam emission from the electron emission layer 23. The high voltage provided by the anode conductive layer 12 accelerates the electron beam with sufficient momentum to impinge the phosphors layer 13 of the anode plate 10, which is then excited to emit a light.
The lately developed carbon nanotube has been applied to form the electron-emission source of a field-emission display due to its specific characteristics. The carbon nanotube is typically formed on a cathode plate for generating electron beams. Currently, the carbon-nanotube electron-emission source is formed by screen printing and has viscosity as high as 100,000 cps. With such high viscosity, it is very difficult to obtain an even surface. As a result, the distance between the electron-emission layer and the gate layer of the same cathode unit is non-uniform, such that the electric field cannot be uniform to generate uniform electron beams in each position. That is, when the gap between the electron-emission layer and the gate layer is shorter, the electric field is larger, and more electrons are emitted. The very high viscosity of the carbon nanotube mixture is very difficult to distribute. Therefore, dispersing technique based on its mechanism and physical property has is required. Even when the carbon nanotube mixture is distributed by mechanical and physical property, an even thickness is still difficult to obtain. Therefore, non-uniform electron beams are emitted. As a result, uneven brightness in a single luminescent unit occurs, such that the image quality is degraded. In addition, although the carbon nanotube mixture has very high viscosity, the adhesion is insufficient. Therefore, adhesion additive such as glass powder is often required to further complicate the process.